1. Field of the Invention
The present invention relates to a non-reciprocal circuit element which is used in a microwave band, and more particularly, it relates to a structure of a high frequency non-reciprocal circuit element (i.e., one used in high frequency applications) which is usable in a circulator, an isolator or the like, for example.
2. Description of the Background Art
In recent years, high-frequency devices have been increasingly miniaturized and generalized in a mobile communication system or the like. It has therefor become necessary to reduce the size and cost of non-reciprocal circuit elements employed in such devices.
Such a non-reciprocal circuit element includes the so-called lumped parameter non-reciprocal circuit element having a plurality of center electrodes which are arranged to intersect with each other in an electrically insulated state, and high frequency-use magnetic bodies which are arranged on upper and lower sides of the plurality of center electrodes arranged so that do magnetic fields are applied to the plurality of center electrodes by permanent magnets, for example. Examples of such an element are a lumped parameter type circulator, an isolator and the like.
An exemplary method of manufacturing the aforementioned high frequency non-reciprocal circuit element is now described with reference to FIG. 13. A center electrode 32a is arranged on a disk shaped high frequency-use magnetic body 31a. The center electrode 32a radially extends through the center of an upper surface of the high frequency-use magnetic body 31a, to reach a side surface of the high frequency-use magnetic body 31a. Then, an insulating film 33a of an insulating material is arranged on the center electrode 32a, and another center electrode 32b is arranged thereon to intersect with the center electrode 32a. An insulating film 33b, a center electrode 32c and an insulating film 33c are successively arranged on the center electrode 32b, and a high frequency-use magnetic body 31b is finally placed on and fixed to such a structural body. Thereafter permanent magnets are arranged on upper and lower side of the thus-obtained structure, to apply de magnetic fields to the structural body which is held between the high frequency-use magnetic bodies 31a and 31b.
In order to manufacture such a conventional high frequency non-reciprocal circuit element, the center electrodes 32a to 32c are manually arranged alternately with the insulating films 33a to 33c, as described above with reference to FIG. 13. However, it is extremely difficult to manually assemble the center electrodes 32a to 32c, which are reduced to about several millimeters in length with miniaturization of the high frequency non-reciprocal circuit element. In a miniature high frequency non-reciprocal circuit element, therefore, imperfect assembling such as relative misregistration of the center electrodes 32a to 32c is so frequently caused that it is difficult to obtain a highly reliable high frequency non-reciprocal circuit element.
Further, the manufacturing cost for such a conventional circuit element is increased due to frequent imperfect assembling caused by manual assembling.
While the high frequency non-reciprocal circuit element requires a relatively large number of components as hereinabove described, it is difficult to reduce the cost therefor due to restriction in cost reduction for the respective components.